Dr. Alyssa K. Betts, Extension Field Crops Pathologist; akoehler@udel.edu
Heading in barley is underway and wheat is flag leaf to boot stage. Although it has been wet, the rains are slowing, and we are currently at low risk in the Fusarium Risk Tool (Figure 1). Barley starts flowering prior to heading, while wheat usually starts to flower 3-4 days after heading out (Figure 2). If you are planning for wheat fungicide application, scout frequently and apply when wheat is flowering (Feekes 10.5.1). Weather can impact how many days from when heads become visible until flowering actually begins. Look for yellow anthers in the center of the wheat head to signal the start of flowering (Figure 2). Some years it may be 3-4 days while others I have waited 10-11 days. Once wheat is flowering, fungicides are most effective when applied within 4-5 days. For best mycotoxin (DON) control, it is better to be at flowering or a few days beyond than to spray too early when heads are not out yet. Anthers can remain attached after flowering but become a pale white. Fungicide products should be applied at the manufacturers recommended rate with nozzles angled 30-45° from horizontal (30 degrees is better than 45). Nozzles angled both forward and backward or twinjet nozzles that spray in two directions give better contact with the head and increase fungicide efficacy. For ground sprays, fungicides should be applied in at least 10-15 gallons of water per acre; aerial applications are recommended at 5 gallons per acre.
Figure 1: FHB Risk Model for April 18, 2024 (wheatscab.psu.edu)
Figure 2: Wheat at flowering (Feekes 10.5.1) with yellow anthers visible 3-4 days after heads emerge.